Publications
175 results found
Baker G, White A, Casely I, et al., 2022, Catalytic, Z-Selective, Semi-Hydrogenation of Alkynes with a Zinc–Anilide Complex
<jats:p>The reversible activation of dihydrogen with a molecular zinc anilide complex is reported. The mechanism of this reaction has been probed through stoichiometric experiments and DFT calculations. The combined evidence suggests that H2 activation occurs by addition across the Zn–N bond via a four-membered transition state in which the Zn and N atoms play a dual role of Lewis acid and Lewis base. The zinc hydride complex that results from H2 addition, has been shown to be remarkably effective for the hydrozincation of C=C bonds at modest temperatures. The scope of hy-drozincation includes alkynes, alkenes, and a 1,3-butadiyne. For alkynes, the hydrozincation step is stereospecific leading exclusively to the syn-isomer. Competition experiments show that the hydrozincation of alkynes is faster than the equivalent alkene substrates. These new discoveries have been used to develop an unprecedented catalytic sys-tem for the semi-hydrogenation of alkynes. The catalytic scope includes both aryl and alkyl substituted internal al-kynes and proceeds with high alkene : alkane (>91 : 9) and Z : E ratios (>96 : 4). This work offers a first example of selective hydrogenation catalysis using zinc complexes.</jats:p>
Parr JM, White AJP, Crimmin MR, 2022, Magnesium-stabilised transition metal formyl complexes: structures, bonding, and ethenediolate formation, CHEMICAL SCIENCE, Vol: 13, Pages: 6592-6598, ISSN: 2041-6520
- Author Web Link
- Cite
- Citations: 7
Rekhroukh F, Zhang L, Kong R, et al., 2022, Stereoselective Insertion of Cyclopropenes into Mg–Mg Bonds
<jats:p>The reaction of cyclopropenes with compounds containing Mg–Mg bonds is reported. 1,2-Dimagnesiation occurs exclusively by syn-addition to the least hindered face of the alkene forming a single diastereomeric product. DFT calculations support a concerted and stereoselective mechanism. These findings shed new light on the stereochemistry of reactions involving magnesium reagents.</jats:p>
Gorgas N, White AJP, Crimmin MR, 2022, Cooperative C-H Bond Activation by a Low-Spin d<SUP>6</SUP> Iron-Aluminum Complex, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol: 144, Pages: 8770-8777, ISSN: 0002-7863
- Author Web Link
- Cite
- Citations: 12
Garçon M, Phanopoulos A, Sackman G, et al., 2022, The Continuum Between Hexagonal Planar and Trigonal Planar Geometries
<jats:p>New heterometallic hydride complexes that involve the addition of {Mg–H} and {Zn–H} bonds to group 10 transition metals (Pd, Pt) are reported. The side-on coordination of a single {Mg–H} to Pd forms a well-defined σ-complex. In contrast, addition of three {Mg–H} or {Zn–H} bonds to Pd or Pt results in the formation of planar complexes with subtly different geometries. We compare their structures through experiment (X-ray diffraction, neutron diffraction, multinuclear NMR), computational methods (DFT, QTAIM, NCIPlot), and theoretical analysis (MO diagram, Walsh diagram). These species can be described as snapshots along a continuum of bonding between ideal trigonal planar and hexagonal planar geometries.</jats:p>
Garçon M, Phanopolous A, Sackman G, et al., 2022, The Continuum Between Hexagonal Planar and Trigonal Planar Geometries
<jats:p>New heterometallic hydride complexes that involve the addition of {Mg–H} and {Zn–H} bonds to group 10 transition metals (Pd, Pt) are reported. The side-on coordination of a single {Mg–H} to Pd forms a well-defined σ-complex. In contrast, addition of three {Mg–H} or {Zn–H} bonds to Pd or Pt results in the formation of planar complexes with subtly different geometries. We compare their structures through experiment (X-ray diffraction, neutron diffraction, multinuclear NMR), computational methods (DFT, QTAIM, NCIPlot), and theoretical analysis (MO diagram, Walsh diagram). These species can be described as snapshots along a continuum of bonding between ideal trigonal planar and hexagonal planar geometries.</jats:p>
Mulryan D, Rodwell J, Phillips NA, et al., 2022, Au(I) Catalyzed HF Transfer: Tandem Alkyne Hydrofluorination and Perfluoroarene Functionalization, ACS CATALYSIS, Vol: 12, Pages: 3411-3419, ISSN: 2155-5435
- Author Web Link
- Cite
- Citations: 8
Batuecas M, Kong RY, White AJP, et al., 2022, Functionalization and hydrogenation of carbon chains derived from CO, Angewandte Chemie International Edition, Vol: 61, ISSN: 1433-7851
Selective reactions that combine H 2 , CO and organic electrophiles (aldehyde, ketones, isocyanide) to form hydrogenated C 3 and C 4 carbon chains are reported. These reactions proceed by CO homologation mediated by [W(CO) 6 ] and an aluminum(I) reductant, followed by functionalization and hydrogenation of the chain ends. A combination of kinetics (rates, KIEs) and DFT calculations has been used to gain insight into a key step which involves hydrogenation of a metallocarbene intermediate. These findings expand the extremely small scope of systems that combine H 2 and CO to make well-defined products with complete control over chain length and functionality.
Gorgas N, White A, Crimmin M, 2022, Cooperative C–H Bond Activation by a Low-Spin d6 Iron–Aluminium Complex
<jats:p>The reactions of transition metal complexes underpin numerous synthetic processes and catalytic transformations. Typically, this reactivity involves the participation of empty and filled molecular orbitals centred on the transition metal. Kinetically stabilised species, such as octahedral low-spin d6 transition metal complexes, are not expected to participate directly in these reactions. However, novel approaches that exploit metal ligand-cooperativity offer an opportunity to challenge these preconceptions. Here we show that inclusion of an aluminium-based ligand into the coordination sphere of neutral low-spin d6 iron complex leads to unexpected reactivity. Complexes featuring an unsupported Fe–Al bond are capable of the intermolecular C–H bond activation of pyridines. Mechanistic analysis suggests that C–H activation proceeds through a reductive deprotonation in which the two metal centres (Fe and Al) act like a frustrated Lewis-pair. Key to this behaviour is a ground state destabilisation of the d6 iron complex, brought about by the inclusion of the electropositive aluminium-based ligand. These findings have immediate implications for the design of reagents and catalysts based on 1st row transition metals.</jats:p>
Gorgas N, White A, Crimmmin M, 2022, Cooperative C–H Bond Activation by a Low-Spin d6 Iron–Aluminium Complex
<jats:p>The reactions of transition metal complexes underpin numerous synthetic processes and catalytic transformations. Typically, this reactivity involves the participation of empty and filled molecular orbitals centred on the transition metal. Kinetically stabilised species, such as octahedral low-spin d6 transition metal complexes, are not expected to participate directly in these reactions. However, novel approaches that exploit metal ligand-cooperativity offer an opportunity to challenge these preconceptions. Here we show that inclusion of an aluminium-based ligand into the coordination sphere of neutral low-spin d6 iron complex leads to unexpected reactivity. Complexes featuring an unsupported Fe–Al bond are capable of the intermolecular C–H bond activation of pyridines. Mechanistic analysis suggests that C–H activation proceeds through a reductive deprotonation in which the two metal centres (Fe and Al) act like a frustrated Lewis-pair. Key to this behaviour is a ground state destabilisation of the d6 iron complex, brought about by the inclusion of the electropositive aluminium-based ligand. These findings have immediate implications for the design of reagents and catalysts based on 1st row transition metals.</jats:p>
Batuecas M, Kong R, White A, et al., 2021, Functionalization and Hydrogenation of Carbon Chains Derived from CO
<jats:p>Selective reactions that combine H2, CO and organic electrophiles (aldehyde, ketones, isocyanide) to form hydrogenated C3 and C4 carbon chains are reported. These reactions proceed by CO homologation mediated by [W(CO)6] and an aluminum(I) reductant, followed by functionalization and hydrogenation of the chain ends. A combination of kinetics (rates, KIEs) and DFT calculations has been used to gain insight into a key step which involves hydrogenation of a metallocarbene intermediate. These findings expand the extremely small scope of systems that combine H2 and CO to make well-defined products with complete control over chain length and functionality.</jats:p>
Mulryan D, Rodwell J, Phillips N, et al., 2021, Au(I) Catalyzed HF Transfer: Tandem Alkyne Hydrofluorination and Perfluoroarene Functionalisation
<jats:p>HF transfer reactions between organic substrates are an incredibly rare class of transformation. Such reactions require the development of new catalytic systems that can promote both defluorination and fluorination steps in a single reaction sequence. Herein, we report a novel catalytic protocol in which an equivalent of HF is generated from a perfluoroarene | nucleophile pair and transferred directly to an alkyne. The reaction is catalysed by [Au(IPr)NiPr2] (IPr = N,N’-1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene) and is 100 % atom efficient. HF transfer generates two useful products in the form of functionalised fluoroarenes and fluoroalkenes. Mechanistic studies (rate laws, KIEs, DFT calculations, competition experiments) are consistent with the Au(I) catalyst facilitating a catalytic network involving both concerted SNAr and hydrofluorination steps. The nature of the nucleophile impacts the turnover-limiting step. The cSNAr step is turnover-limiting for phenol-based nucleophiles while proteodeauration likely becomes turnover-limiting for aniline-based nucleophiles. The new approach removes the need for direct handling of HF reagents in hydrofluorination and offers new possibilities to manipulate the fluorine content of organic molecules through catalysis.</jats:p>
Kong RY, Batuecas M, Crimmin MR, 2021, Reactions of aluminium(i) with transition metal carbonyls: scope, mechanism and selectivity of CO homologation, CHEMICAL SCIENCE, Vol: 12, Pages: 14845-14854, ISSN: 2041-6520
- Author Web Link
- Cite
- Citations: 12
Brown R, Hooper TN, Rekhroukh F, et al., 2021, Alumination of aryl methyl ethers: switching between sp 2 and sp 3 C–O bond functionalisation with Pd-catalysis, Chemical Communications, Vol: -, Pages: 1-4, ISSN: 1359-7345
The reaction of [{(ArNCMe)2CH}Al] (Ar = 2,6-di-iso-propylphenyl) with aryl methyl ethers proceeded with alumination of the sp3 C–O bond. The selectivity of this reaction could be switched by inclusion of a catalyst. In the presence of [Pd(PCy3)2], chemoselective sp2 C–O bond functionalisation was observed. Kinetic isotope experiments and DFT calculations support a catalytic pathway involving the ligand-assisted oxidative addition of the sp2 C–O bond to a Pd–Al intermetallic complex.
Parr J, White AJP, Crimmin M, 2021, Magnesium-Stabilised Transition Metal Formyl Complexes: Structures, Bonding, and Ethenediolate Formation
<jats:p>Herein we report the first comprehensive series of crystallographically characterised transition metal formyl complexes. In these complexes, the formyl ligand is trapped as part of a chelating structure between a transition metal (Cr, Mn, Fe, Co, Rh, W, and Ir) and a magnesium (Mg) cation. Calculations suggest that this bonding mode results in significant oxycarbene-character of the formyl ligand. Electron-rich late-transition metal complexes have the highest oxycarbene-character to the bonding and are the most stable in solution. Further reaction of a heterometallic Cr---Mg formyl complex results in a rare example of C–C coupling and formation of an ethenediolate complex. These results show that well-defined transition metal formyl complexes are potential intermediates in the homologation of carbon monoxide.</jats:p>
Parr J, White AJP, Crimmin M, 2021, Magnesium-Stabilised Transition Metal Formyl Complexes: Structures, Bonding, and Ethenediolate Formation
<jats:p>Herein we report the first comprehensive series of crystallographically characterised transition metal formyl complexes. In these complexes, the formyl ligand is trapped as part of a chelating structure between a transition metal (Cr, Mn, Fe, Co, Rh, W, and Ir) and a magnesium (Mg) cation. Calculations suggest that this bonding mode results in significant oxycarbene-character of the formyl ligand. Electron-rich late-transition metal complexes have the highest oxycarbene-character to the bonding and are the most stable in solution. Further reaction of a heterometallic Cr---Mg formyl complex results in a rare example of C–C coupling and formation of an ethenediolate complex. These results show that well-defined transition metal formyl complexes are potential intermediates in the homologation of carbon monoxide.</jats:p>
Crimmin MR, 2021, Benzene rings reach their breaking point, NATURE, Vol: 597, Pages: 33-34, ISSN: 0028-0836
- Author Web Link
- Cite
- Citations: 1
Kong R, Batuecas M, Crimmin M, 2021, Reactions of Aluminium(I) with Transition Metal Carbonyls: Scope, Mechanism and Selectivity of CO Homologation
<jats:p>Over the past few decades, numerous model systems have been discovered that create carbon–carbon bonds from CO. These reactions are of potential relevance to the Fischer-Tropsch (F-T) process, a technology that converts syngas mixtures (H2/CO) into mixtures of hydrocarbons. In this paper, a new homogeneous model system that constructs carbon chains from CO is reported. The system exploits the cooperative effect of a transition metal complex and main group reductant. An entire reaction sequence from C1 to C2 to C3 to C4 has been synthetically verified. The scope of reactivity is broad and includes a variety of transition metals (M = Cr, Mo, W, Mn, Re, Co), including those found in industrial heterogeneous F-T catalysts. Variation of the transition metal fragment impacts the relative rate of the steps of chain growth, allowing isolation and structural characterisation of a rare C2 intermediate. The selectivity of carbon chain growth is also impacted by this variable; two distinct isomers of the C3 carbon chain were observed to form in different ratios with different transition metal reagents. Based on a combination of experiments (isotope labelling studies, study of intermediates) and calculations (DFT, NBO, ETS-NOCV) we propose a complete mechanism for chain growth that involves defined reactivity at both transition metal and main group centres.</jats:p>
Kong R, Batuecas M, Crimmin M, 2021, Reactions of Aluminium(I) with Transition Metal Carbonyls: Scope, Mechanism and Selectivity of CO Homologation
<jats:p>Over the past few decades, numerous model systems have been discovered that create carbon–carbon bonds from CO. These reactions are of potential relevance to the Fischer-Tropsch (F-T) process, a technology that converts syngas mixtures (H2/CO) into mixtures of hydrocarbons. In this paper, a new homogeneous model system that constructs carbon chains from CO is reported. The system exploits the cooperative effect of a transition metal complex and main group reductant. An entire reaction sequence from C1 to C2 to C3 to C4 has been synthetically verified. The scope of reactivity is broad and includes a variety of transition metals (M = Cr, Mo, W, Mn, Re, Co), including those found in industrial heterogeneous F-T catalysts. Variation of the transition metal fragment impacts the relative rate of the steps of chain growth, allowing isolation and structural characterisation of a rare C2 intermediate. The selectivity of carbon chain growth is also impacted by this variable; two distinct isomers of the C3 carbon chain were observed to form in different ratios with different transition metal reagents. Based on a combination of experiments (isotope labelling studies, study of intermediates) and calculations (DFT, NBO, ETS-NOCV) we propose a complete mechanism for chain growth that involves defined reactivity at both transition metal and main group centres.</jats:p>
Sheldon DJ, Crimmin MR, 2021, Complete deconstruction of SF<sub>6</sub> by an aluminium(i) compound, CHEMICAL COMMUNICATIONS, Vol: 57, Pages: 7096-7099, ISSN: 1359-7345
- Author Web Link
- Cite
- Citations: 13
Sheldon D, Crimmin M, 2021, Complete Deconstruction of SF6 by an Aluminium(I) Compound
<jats:p><jats:bold>The room-temperature activation of SF<jats:sub>6</jats:sub>, a potent greenhouse gas, is reported using a monovalent aluminium(I) reagent to form well-defined aluminium(III) fluoride and aluminium(III) sulfide products. New reactions have been developed to utilise the aluminium(III) fluoride and aluminium(III) sulfide as a nucleophilic source of F<jats:sup>–</jats:sup> and S<jats:sup>2– </jats:sup>for a range of electrophiles. The overall reaction sequence results in the net transfer of fluorine or sulfur atoms from an environmentally detrimental gas to useful organic products.</jats:bold></jats:p>
Brown R, hooper TN, Rekroukh F, et al., 2021, Alumination of Aryl Methyl Ethers: Switching Between Sp2 and Sp3 C–O Bond Functionalisation with Pd-Catalysis
<jats:p>The reaction of [{(ArNCMe)2CH}Al] (Ar = 2,6-di-iso-propylphenyl, 1) with aryl methyl ethers proceeded with alumination of the sp3 C–O bond by a presumed SN2 pathway. The selectivity of this reaction could be switched by inclusion of a catalyst. In the presence of [Pd(PCy3)2], chemoselective sp2 C–O bond functionalisation was observed. Kinetic isotope experiments and DFT calculations support a catalytic pathway involving the ligand-assisted oxidative addition of the sp2 C–O bond to a Pd---Al intermetallic complex. The net result of both non-catalysed and catalytic pathways is the generation of polar organoaluminium complexes from aryl methyl ethers with complete atom-efficiency. Switches in selectivity yield isomeric products from a single starting material. The methodology (and mechanistic insight) holds promise as a means to functionalise aromatic molecules derived from lignin depolymerisation and we demonstrate an application to a derivative of vanillin.</jats:p>
Phillips NA, Kong RY, White AJP, et al., 2021, Group 11 Borataalkene Complexes: Models for Alkene Activation, Angewandte Chemie, Vol: 133, Pages: 12120-12126, ISSN: 0044-8249
<jats:title>Abstract</jats:title><jats:p>A series of linear late transition metal (M=Cu, Ag, Au and Zn) complexes featuring a side‐on [B=C]<jats:sup>−</jats:sup> containing ligand have been isolated and characterised. The [B=C]<jats:sup>−</jats:sup> moiety is isoelectronic with the C=C system of an alkene. Comparison across the series shows that in the solid‐state, deviation between the η<jats:sup>2</jats:sup> and η<jats:sup>1</jats:sup> coordination mode occurs. A related zinc complex containing two [B=C]<jats:sup>−</jats:sup> ligands was prepared as a further point of comparison for the η<jats:sup>1</jats:sup> coordination mode. The bonding in these new complexes has been interrogated by computational techniques (QTAIM, NBO, ETS‐NOCV) and rationalised in terms of the Dewar–Chatt–Duncanson model. The combined structural and computational data provide unique insight into catalytically relevant linear d<jats:sup>10</jats:sup> complexes of Cu, Ag and Au. Slippage is proposed to play a key role in catalytic reactions of alkenes through disruption and polarisation of the π‐system. Through the preparation and analysis of a consistent series of group 11 complexes, we show that variation of the metal can impact the coordination mode and hence substrate activation.</jats:p>
Phillips N, Kong R, White A, et al., 2021, Slippage between η2 and η1 coordination in Group 11 borataalkene complexes: models for alkene activation, Angewandte Chemie International Edition, Vol: 60, Pages: 12013-12019, ISSN: 1433-7851
A series of linear late transition metal (M = Cu, Ag, Au and Zn) complexes featuring a side-on [B=C] - containing ligand have been isolated and characterised. The [B=C] - moiety is isoelectronic with the C=C system of an alkene. Comparison across the series shows that in the solid-state, deviation between the η 2 and η 1 coordination mode occurs. The degree of slippage is greatest for Au > Ag > Cu. A related zinc complex containing two [B=C] - ligands was prepared as a further point of comparison for the η 1 coordination mode. The bonding in these new complexes has been interrogated by computational techniques (QTAIM, NBO, ETS-NOCV) and rationalised in terms of the Dewar-Chatt-Duncanson model. The combined structural and computational data provide unique insight into catalytically relevant linear d 10 complexes of Cu, Ag and Au. Slippage is proposed to play a key role in catalytic reactions of alkenes through disruption and polarisation of the p -system. Through the preparation and analysis of a consistent series of group 11 complexes, we show that variation of the metal can impact the degree of slippage and hence substrate activation.
Kong RY, Crimmin MR, 2021, 1(st) row transition metal aluminylene complexes: preparation, properties and bonding analysis, Dalton Transactions: an international journal of inorganic chemistry, Vol: 50, Pages: 7810-7817, ISSN: 1477-9226
The synthesis and spectroscopic characterisation of eight new first-row transition metal (M = Cr, Mn, Fe, Co, Cu) aluminylene complexes is reported. DFT and ab initio calculations have been used to provide detailed insight into the metal–metal bond. The σ-donation and π-backdonation properties of the aluminylene ligand are evaluated via NBO and ETS-NOCV calculations. These calculations reveal that these ligands are strong σ-donors but also competent π-acceptors. These properties are not fixed but vary in response to the nature of the transition metal centre, suggesting that aluminylene fragments can modulate their bonding to accommodate both electron-rich and electron-poor transition metals. Ab initio DLPNO-CCSD(T) calculations show that dispersion plays an important role in stabilising these complexes. Both short-range and long-range dispersion interactions are identified. These results will likely inform the design of next-generation catalysts based on aluminium metalloligands.
Kong RY, Crimmin M, 2021, 1st Row Transition Metal Aluminylene Complexes: Preparation, Properties and Bonding Analysis
<jats:p><jats:italic>The synthesis and spectroscopic characterisation of eight new first-row transition metal (M = Cr, Mn, Fe, Co, Cu) aluminylene complexes is reported. DFT and ab<jats:bold> </jats:bold>initio calculations have been used to provide detailed insight into the metal–metal bond. The σ-donation and π-backdonation properties of the aluminylene ligand are evaluated via NBO and ETS-NOCV calculations. These calculations reveal that these ligands are strong σ-donors but also competent π-acceptors. These properties are not fixed but vary in response to the nature of the transition metal centre, suggesting that aluminylene fragments can modulate their bonding to accommodate both electron-rich and electron-poor transition metals. Ab initio<jats:bold> </jats:bold>DLPNO-CCSD(T) calculations show that dispersion plays an important role in stabilising these complexes. Both short-range and long-range dispersion interactions are identified. These results will likely inform the design of next-generation catalysts based on aluminium metalloligands. </jats:italic></jats:p>
Garçon M, Mun NW, White AJP, et al., 2021, Palladium-catalysed C-H bond zincation of arenes: scope, mechanism, and the role of heterometallic intermediates, Angewandte Chemie International Edition, Vol: 60, Pages: 6145-6153, ISSN: 1433-7851
Catalytic methods that transform C-H bonds into C-X bonds are of paramount importance in synthesis. A particular focus has been the generation of organoboranes, organosilanes and organostannanes from simple hydrocarbons (X=B, Si, Sn). Despite the importance of organozinc compounds (X=Zn), their synthesis by the catalytic functionalisation of C-H bonds remains unknown. Herein, we show that a palladium catalyst and zinc hydride reagent can be used to transform C-H bonds into C-Zn bonds. The new catalytic C-H zincation protocol has been applied to a variety of arenes-including fluoroarenes, heteroarenes, and benzene-with high chemo- and regioselectivity. A mechanistic study shows that heterometallic Pd-Zn complexes play a key role in catalysis. The conclusions of this work are twofold; the first is that valuable organozinc compounds are finally accessible by catalytic C-H functionalisation, the second is that heterometallic complexes are intimately involved in bond-making and bond-breaking steps of C-H functionalisation.
Garçon M, Mun NW, White AJP, et al., 2021, Palladium‐Catalysed C−H Bond Zincation of Arenes: Scope, Mechanism, and the Role of Heterometallic Intermediates, Angewandte Chemie, Vol: 133, Pages: 6210-6218, ISSN: 0044-8249
<jats:title>Abstract</jats:title><jats:p>Catalytic methods that transform C−H bonds into C−X bonds are of paramount importance in synthesis. A particular focus has been the generation of organoboranes, organosilanes and organostannanes from simple hydrocarbons (X=B, Si, Sn). Despite the importance of organozinc compounds (X=Zn), their synthesis by the catalytic functionalisation of C−H bonds remains unknown. Herein, we show that a palladium catalyst and zinc hydride reagent can be used to transform C−H bonds into C−Zn bonds. The new catalytic C−H zincation protocol has been applied to a variety of arenes—including fluoroarenes, heteroarenes, and benzene—with high chemo‐ and regioselectivity. A mechanistic study shows that heterometallic Pd–Zn complexes play a key role in catalysis. The conclusions of this work are twofold; the first is that valuable organozinc compounds are finally accessible by catalytic C−H functionalisation, the second is that heterometallic complexes are intimately involved in bond‐making and bond‐breaking steps of C−H functionalisation.</jats:p>
Batuecas M, Gorgas N, Crimmin MR, 2021, Catalytic C-H to C-M (M = Al, Mg) bond transformations with heterometallic complexes, CHEMICAL SCIENCE, Vol: 12, Pages: 1993-2000, ISSN: 2041-6520
- Author Web Link
- Cite
- Citations: 17
Kong RY, Crimmin MR, 2021, Chemoselective C-C σ-bond activation of the most stable ring in biphenylene., Angewandte Chemie International Edition, Vol: 60, Pages: 2619-2623, ISSN: 1433-7851
The chemoselective cleavage of a six-membered aromatic ring in biphenylene is reported using an aluminium(I) complex. This type of selectivity is unprecedented. In every example of transition metal mediated C-C sigma-bond activation reported to date, the reaction occurs at the central four-membered ring of biphenylene. Insight into the origin of chemoselecitivty was obtained through a detailed mechanistic analysis (isolation of an intermediate, DFT studies, activation strain analysis). We conclude that the divergent reactivity can be attributed to differences in both the symmetry and radial extension of the frontier molecular orbitals of the aluminium(I) fragment compared to common transition metal fragments.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.